Cooling - Hull water pickup
 

I was looking for some help in verifying whether the water pickup I'm using is going to be large enough
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1. engine is 502 or 556 ci Chev BB, it will be N.A. or turbocharged
2. I intend to use mercruiser closed water system, and install larger expansion tank
3. the mercury performance engine sump is 12 litre capacity
4. the exhaust will be sea water cooled to ensure the closed water system cools engine without adding the extra heat from exhaust
5. the external water will be cooling engine cooler, hydraulic power steering cooler, exhaust cooling, and HX cooling
6. Sea pump: was going to use Jabsco crank mount pump, or Mercruiser 46807151, or after market pump. As far as I can make out the Jabsco, and Mercruiser pump output is approx. 25 gallons (100 litres/min) @ 4000 rpm
6. I have used 1.25" claim shell water pickup, ball valve Hose 1.5: (1.25" ID)
7. The claim shell external water pickup is 16" from transom, and 6" off centre

Questions
A. Do I need to modify the claim to remove some of the grate, to increase the flow surface area?
B. will one pickup be sufficient, or do I need to add another pickup?
C. some of the time I imagine back of boat will be out of water, so wondering how the sea pump will handle this?

cheers
Brett
:

Is that the bottom of a strainer the pickup its plumbed to ?

yes that's correct

mine feed in the top and exit the bottom.... not sure where the filter screen is located in yours

found a few more pics of the strainer itself
The strainer is cylindrical, water comes up inside of strainer and moves through to outside of bowl
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I see, that makes sense now I see it apart, I dont think you will have any issues with water volume but its hard to tell the width of the slits in the pickup

The slits are 2.3 wide x75mm long = 172mm = 0.266 square inches x 7 slits = 1.86 " (1207mm2)

If incoming water supply is through 1.25" (32mm ) Dia strainer
Then assuming my calcs are correct 38mm/2 = 16mm Radius
16mm x 16mm x 3.142 = 804mm 2
so looks like it may delivery sufficient water
Perhaps strainer is a little on small size to hold sufficient water, although not sure?

I know guys running 2 stage pumps to large inter coolers and the engine through a single 1.25 hose

my concern is the claim shell water pickup and whether at speed it will pick up water
I suppose I could increase the size of 2 of the split by removing some of the casting, that should increase surface area by 25%
I wonder if anyone else running these water pickups?

ya, most are transom mount and get force fed @ speed

ALL wakeboats use this exact water intake grate. The have alot less water aeration than transom installed water pick ups -- especially in step hull apps for whomever has installed this grate. -- bottom of the hull.

I understand that many sportboats use transom water pick ups.

The thing you have to watch out for -- the grate is NOT installed too far forward in the bottom that has alot of hull / bow lift. Wakeboats do not have to worry about any of that. Nor installed to far outside as the faster the boat goes -- the more, the hull comes out of the water.

I would use the grate that has a 1.25 ID fitting and hose connections. There is other styles available to offer more volume water as well. Some are called persay performance grates as well.

BUP / AusScarab29
Thanks for your comments
Perhaps I'm being a little paranoid and over thinking the issue
Maybe I just will open up 2 of the slots and then judge water happens after that
I assume if I start losing sea water pump impellers we know its not getting sufficient water

I get a couple per year with the same water grate set up for V hull sportboats I/O s. Past week had a 25 ft Checkmate come in with a big block, the same set up for winterization. Good thing smart enough to look how the set up is before I hook up the water hose and muffs to the outdrive. Use the same water flush / water hose as the wakeboats to run the engine(s). No difference for running on the hose vs wakeboats. .

the plunger aka water flusher and its adjustable in length

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BUP
The mother of all plungers
Did you glue the fitting on side for hose connection or you buy it ready to go?

they ALL come that way. I have 5 of the exact same ones. Buy a quality one because it makes all the difference in the world.

screw water hose on FIRST -- then creeper under the boat trailer and then set it up tightly fit around the grate to the ground --

BUP
okay found it
cheers
Brett

I thought only slow boats used those pick ups , never seen one on a powerboat.
I would think that thing is going to cost you some speed.
Why not a standard pickup like everyone else uses?
I like Imcos adjustable pickups, at the transom there`s only about 1/4" sticking past the hull and I can dial in my pressure.

yes the boat is going slow at present as its on trailer and yet to get christened
I was concerned about the water turbulence in front of the Arneson drive so tucked the water pickup under the boat
Not sure whether this was the right thing to do, given the boat is only 21.5'
However time will tell
cheers

Surface drive are further back then your standard drive and props halfway out of the water , not affected so much by "turbulence"
I think you`ll be fighting high water pressure issues and have no way to adjust the pickup/pressure.
Transom pickups you can cut/adjust shorter . Took me 2 weekends to dial mine in ( had to keep cutting it back) and I still have to run blow offs to keep pressure under 20 psi@wot.
I always thought those pickups are more for AC`s , live wells, wake boats, cruisers. I could be wrong.


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not a whole lot in the water

Some wake boats have stepped hulls - single stepped, there is some wake boats 60 mph but most are a solid 45 to 50 all day long. they have no issues with cooling using that grate.

There is many inboards - inboards cabin boats - and so on that use the same set up.

The fastest boat I drove using the grate set up was 77 mph so thats what I know in person. . V hull - 24 degree single modied big block w/ bravo / nose cone.

ICDEDPPL

can you advise how you were able to control the pressure of water coming through pickup
Out of curiosity how did you have pressure gauge hooked up, and kept lifting the height of the transom mounted pickup until you achieved around 20 psi

The fresh water pick-ups that I am using are adjustable transom mounted ones I got from Hardin Marine , when I got my water pressure to where I wanted it I welded the slide part together so it would not move .

The picture I posted is where I started.(pre existing hole thru transom)
Put in water go for a spin , back on trailer , use a band saw to shorten pick up in tiny increments , repeat till pressure was where I wanted it to be.

I have pressure gauges on both engines on dash.

ICDEDPPL / Green lightning

Im running closed water system, and need sea cooler to cool exchanger etc.

1. where do you tap into to check the water pressure, is it before or after strainer,
2. if anyone has picture of the step up would be good to learn

cheers
Brett

Looked at your other thread in the fiberglass section for more pics.
You have the pickup mounted 10 inches from the centerline and 16 inches from the transom.

Probably an optical illusion and probably i'm wrong but if the bottom is flat/flattish w/ an edge
My concern would be aeration in the area of the pickup from water leaving the pad.
How about a picture looking forward at the transom so we can see the pickup and the contours of the bottom
Again, i`m probably way off, just hate to see you have to move the pickup after the boat is all together.

My tap for my pressure gauges is on my engines they are installed in one of the block drain holes

In a closed cooling system you want to know how much water pressure the heat ex changer is seeing because the pressure will change when the sea strainer picks up garbage in the water .

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if you look in the right hand corner, the barbed fitting is where I take my reading from. it`s on top of the bellhousing trans cooler...

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dear all
excuse the delay in responding
boat is back on trailer and keel is sitting on trailer bunk, so difficult to actual get a good picture of the underside

Seems I spent too much time inside boat working and didn't take that many pictures of hull, and outside of boat

anyway best pictures of underside, transom and chine attached, some mixed pictures before I repaired transom
The water pickup is 16" from bottom of transom
7" from middle of keel (outside)
The flat section at rear of keel/transom is 11" wide and moves forward approx. 96" and then forward of this keel is a V profile

interested in comments, as many things to do to fit out boat and seems less expensive to do it once, so keen to take on all ideas
Brett


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Brett , How fast do you think your boat's top speed will be , the reason I ask is the faster my boat goes more of of my bow climbs out of the water and that might aerate your pick-up

Just to let you know you have the sea strainer install wrong the intake water always goes in the top port and the engine water comes out the bottom port as to make it more of a gravity feed to the water pump. also that style water pickup doesn't work well at higher speeds because of aeration. and always install the ball valve directly to the pickup you do not want a hose between pickup and valve because if the hose blows you cant shut off the water . Regards Dan

Team Archer green lighning

thanks
refer attached pictures maybe clearer
there is ball valve attached to water pickup on inside of hull, then hose to the strainer
a earlier picture of strainer was attached to the first part of this thread
cant really see how else the strainer will work
The ball valve was changed as can be seen in the picture of the install

as far as speed goes, I'm not sure as boat is not factory made, so no history, I cant even find the guy that built the boat. The chap that I purchased the hull from had the boat sitting in his outboard repair yard for 6 years, and he cant even tell me who he brought the hull from although it was 2200 km away from where we are located
So no history other than use to race with large outboard offshore ski racing in northern Queensland
Done my best to track people down then, then decided to knuckle down and finish the boat as I figure WTF anyway

My idea is in finish the boat, have few motors here, lets put them in and see how hard it runshttps://cimg3.ibsrv.net/gimg/www.off...cab018e2b6.jpg



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I think you have to push the water into the side and pull it from the bottom , by doing that you will have more room for debris and most of the air in the strainer rises to the top so it won,t get pulled into the motor .

I think that if you get the arnesons working good you are going to pick up a lot of air in the strainers https://cimg7.ibsrv.net/gimg/www.off...c510f47164.jpg

That's why you plumb them that way.